Long-chain branched polymers and production processes

ABSTRACT

This invention relates to a process for forming a long-chain branched polymer and a long-chain branched polymer resulting from the process. The process comprises reacting (a) a polyolefin base polymer with (b) a coupling agent comprising a polymeric coupling agent, optionally blended with a molecular coupling agent, the polymeric coupling agent being a modified polyolefin having a reactive coupling group at one or more terminal ends of the modified polyolefin chain, to couple the polyolefin base polymer (a) with the coupling agent (b) to form a long-chain branched polymer having a long-chain branching and/or higher surface energy relative to the polyolefin base polymer.

This application is a Divisional of U.S. patent application Ser. No.15/183,240, filed Jun. 15, 2016, which claims the benefit of priority toU.S. Provisional Patent Application Ser. No. 62/175,670, filed Jun. 15,2015, both of which are hereby incorporated by reference in theirentirety.

FIELD OF THE INVENTION

This invention relates to a novel process for forming a long-chainbranched polymer and a long-chain branched polymer resulting from theprocess.

BACKGROUND OF THE INVENTION

Polypropylene compositions have gained wide commercial acceptance andusage in numerous applications because of the relatively low cost of thepolymers and the desirable properties they exhibit. Commerciallyavailable isotactic polypropylenes are polymers that have a highlylinear structure, have relatively low melt strength, and exhibit poorstrain hardening behavior in the molten state. While these isotacticpolypropylenes are relatively easy to produce, they have very limitedapplications in processes such as thermoforming, foaming, blow molding,film molding, extrusion coating, because of their poor extensionalperformance, poor film toughness properties, and low melt strength.

Polymers containing long-chain branches, on the other hand, have greatvalue in processing techniques that demand high melt strength.

However, there are substantial difficulties in creating long-chainbranched polyolefin, particularly polypropylene. Known routes to producepolypropylene in commercial scale, such as Ziegler-Natta and Metallocenecatalysis, usually produce highly linear and highly stereospecificpolymers. Polymers with a branched or long-chain branched structure havebeen reported using Metallocene catalysts, although there aresignificant limitations in the polymerization process and catalystperformance that impose a challenge for production in commercial scale.

In another example, very small amounts of long-chain branches are knownto be produced and controlled during the polymerization of high densitypolyethylene (HDPE) using chromium catalyst. The amount of branches orlong-chain branches, along with molecular weight (MW) and molecularweight distribution (MWD) are factors to determine the melt elasticityof the polyethylene (PE), which largely defines its commercialprocessing characteristics.

There are also processes to introduce long-chain branches intopolyolefins via post polymerization. For instance, a long-chain branchedpolypropylene can be prepared through a coupling reaction ofpolypropylene and sulfonyl azides. However, there are disadvantagesusing sulfonyl azide chemistries. For example, some sulfonyl azides canbe highly reactive, making reaction control difficult due to therelative lower temperatures (below 140° C.) in which the nitrene radicalis formed, which can consequently lead to an uneven distribution oflinkages in the polypropylene sample. Furthermore, highly reactivesulfonyl azides compounds may increase the risk for explosion and thegeneration of toxic by-products.

There thus remains a need in the art to develop an improved process toprepare polyolefins having long-chain branches that can provide highmelt strength.

SUMMARY OF THE INVENTION

One aspect of the invention relates to a long-chain branched polymerprepared by reacting (a) a polyolefin base polymer with (b) a couplingagent comprising a polymeric coupling agent, optionally blended with amolecular coupling agent, the polymeric coupling agent being a modifiedpolyolefin having a reactive coupling group at one or more terminal endsof the modified polyolefin chain, to couple the polyolefin base polymer(a) with the polymeric coupling agent (b).

Another aspect of the invention relates to a process for forming along-chain branched polymer, comprising reacting (a) a polyolefin basepolymer with (b) a coupling agent comprising a polymeric coupling agent,optionally blended with a molecular coupling agent, the polymericcoupling agent being a modified polyolefin having a reactive couplinggroup at one or more terminal ends of the modified polyolefin chain, tocouple the polyolefin base polymer (a) with the coupling agent (b) toform a long-chain branched polymer.

Another aspect of the invention relates to a long-chain branchedpolymer, comprising a polyolefin base polymer that contains one or morelong-chain branches formed by covalently bonding one or more polymericcoupling agents at one or more binding sites along the polyolefin basepolymer chain.

Another aspect of the invention relates to a process for forming apolymer, comprising reacting (a) a polyolefin base polymer with (b) acoupling agent comprising a polymeric coupling agent, optionally blendedwith a molecular coupling agent, the polymeric coupling agent being amodified polyolefin having a reactive coupling group at one or moreterminal ends of the modified polyolefin chain and a non-reactivefunctional group at one or more terminal ends of the modified polyolefinchain, to couple the polyolefin base polymer (a) with the coupling agent(b) to form a polymer that has a higher surface energy relative to thepolyolefin base polymer and is compatible with inorganic materials.

Additional aspects, advantages and features of the invention are setforth in this specification, and in part will become apparent to thoseskilled in the art on examination of the following, or may be learned bypractice of the invention. The inventions disclosed in this applicationare not limited to any particular set of or combination of aspects,advantages and features. It is contemplated that various combinations ofthe stated aspects, advantages and features make up the inventionsdisclosed in this application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the ¹H NMR spectra of VPN and VPI.

FIG. 2 shows the fourier transform infrared spectroscopy (FTIR) spectraof VPN and VPI.

FIG. 3 is a graph showing the thermogravimetric analysis (TGA)thermograms of VPI and VPN.

FIG. 4 is a graph showing the differential scanning calorimetry (DSC)thermograms of VPN.

FIG. 5 shows the results of size-exclusion chromatography (SEC)measurements of VPI, VPN, and self-coupled VPN.

FIG. 6 shows the ¹³C NMR spectra of VPN and self-coupled VPN.

FIG. 7 shows the ¹H NMR spectra comparing the results of the molecularcoupling agent 4,4′-oxybis(benzenesulfonyl azide) (including theanti-oxidant, pentaerythritoltetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) and theresults of the polymeric coupling agent blend, Blend B1, prepared inExample 2.

FIG. 8 shows the TGA thermograms comparing the T_(onset) of VPI(reference), the polymeric coupling agent (VPN), and the polymericcoupling agent blends (B2 and B3).

FIG. 9 shows the DSC thermogram comparing the thermal behavior ofvarious final polypropylene resins prepared from mixinghomo-polypropylene (HPP) with VPI and VPN against the reference sampleof HPP.

FIG. 10 shows the rheology data comparing the complex viscosity valuesof the final polypropylene resins prepared from mixinghomo-polypropylene (HPP) with VPN against the reference sample of HPP.

FIG. 11 shows the rheology data comparing the tan δ values of the finalpolypropylene resins prepared from mixing homo-polypropylene (HPP) withVPN against the reference sample of HPP.

FIG. 12 shows the rheology data comparing the tan δ values of the finalpolypropylene resins prepared from mixing homo-polypropylene (HPP) withVPN at reaction time between 30 seconds and 180 seconds, against thereference sample of HPP under similar conditions.

FIG. 13 shows the FTIR spectra of the final polypropylene resinsprepared from the coupling reaction between HPP and polymeric couplingagent VPN based on the reaction conditions in P1 or P2 described inExamples 7 and 8, collected at approximately 45 seconds (P1a & P2a), 100seconds (P1b & P2b), 180 seconds (P1c & P2c), 240 seconds (P1d & P2d),360 seconds (P1e & P2e), and 420 seconds (P1f & P2f), respectively.

FIG. 14 shows the FTIP spectra of the final polypropylene resinsprepared from the coupling reaction between HPP and polymeric couplingagent blend B3 and B4 based on the reaction conditions in P3 describedin Example 9, collected at approximately 45 seconds (P3a-B3 and P3a-B4).

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to an improved process to prepare polyolefinshaving long-chain branches. The long-chain branched polymers not onlycontain an increased degree of long-chain branching and different typesof branching in the polymer, but, at the same time, provide improvedperformance in the handling process and improved attributes in the finalpolymer products.

One aspect of the present invention relates to a process for forming along-chain branched polymer. The process comprises reacting (a) apolyolefin base polymer with (b) a coupling agent comprising a polymericcoupling agent being a modified polyolefin having a reactive couplinggroup at one or more terminal ends of the modified polyolefin chain, tocouple the polyolefin base polymer (a) with the coupling agent (b) toform a long-chain branched polymer.

The coupling agent can further comprise a molecular coupling agentblended with the polymeric coupling agent.

Accordingly, another aspect of the present invention relates to aprocess for forming a long-chain branched polymer. The process comprisesreacting (a) a polyolefin base polymer with (b) a coupling agent blendcomprising a polymeric coupling agent blended with a molecular couplingagent, the polymeric coupling agent being a modified polyolefin having areactive coupling group at one or more terminal ends of the modifiedpolyolefin chain, to couple the polyolefin base polymer (a) with thecoupling agent blend to form a long-chain branched polymer.

Another aspect of the invention relates to a process for forming apolymer. The process comprises reacting (a) a polyolefin base polymerwith (b) a coupling agent comprising a polymeric coupling agent,optionally blended with a molecular coupling agent, the polymericcoupling agent being a modified polyolefin having a reactive couplinggroup at one or more terminal ends of the modified polyolefin chain anda non-reactive functional group at one or more terminal ends of themodified polyolefin chain, to couple the polyolefin base polymer (a)with the coupling agent (b) to form a polymer that has a higher surfaceenergy relative to the polyolefin base polymer and is compatible withinorganic materials.

Polyolefin Base Polymer (a)

The coupling reaction can be used to introduce long-chain branches intoany base polymer, polyolefin (a). Suitable polyolefin base polymersinclude polymers having a number average molecular weight of greaterthan 5,000 g/mol, greater than 10,000 g/mol, greater than 20,000 g/mol,greater than 30,000 g/mol, greater than 40,000 g/mol, or greater than50,000 g/mol. Exemplary polyolefin base polymers include those preparedfrom linear or branched α-olefins having 2 to 20 carbon atoms, 2 to 16carbon atoms, or 2 to 12 carbon atoms, including but not limited toethylene, propylene, 1-butene, 2-butene, 1-pentene, 3-methyl-1-butene,1-hexene, 4-methyl-1-pentene, 3-methyl-1-pentene,4,6-dimethyl-1-heptene, 1-octene, 1-decene, 1-undecene, 1-dodecene,1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicocene, and combinationsthereof. These olefins may each contain a heteroatom such as an oxygen,nitrogen, or silicon atom.

The term “polyolefin” generally embraces a homopolymer prepared from asingle type of olefin monomer as well as a copolymer prepared from twoor more olefin monomers. A specific polyolefin referred to herein shallmean polymers comprising greater than 50% by weight of units derivedfrom that specific olefin monomer, including homopolymers of thatspecific olefin or copolymers containing units derived from thatspecific olefin monomer and one or more other types of olefincomonomers. For instance, polypropylene shall mean polymers comprisinggreater than 50 wt % of units derived from propylene monomer, includingpolypropylene homopolymers or copolymers containing units derived frompropylene monomer and one or more other types of olefin comonomers. Thepolyolefin used herein can be a copolymer wherein the comonomer(s)is/are randomly distributed along the polymer chain, a periodiccopolymer, an alternating copolymer, or a block copolymer comprising twoor more homopolymer blocks linked by covalent bonds.

Typical polyolefin base polymers include polyethylene, polypropylene, acopolymer of polyethylene and polypropylene, and a polymer blendcontaining polyethylene, polypropylene, and/or a copolymer ofpolyethylene and polypropylene. For example, the polyolefin base polymer(a) can be polypropylene. The polyolefin base polymer (a) can also bepolyethylene.

The polyolefin base polymer (a) can also be an impact copolymer, i.e., aheterophasic polyolefin copolymer where one polyolefin is the continuousphase and an elastomeric phase is uniformly dispersed therein. Thiswould include, for instance, a heterophasic polypropylene copolymerwhere polypropylene is the continuous phase and an elastomeric phase isuniformly distributed therein. The impact copolymer results from anin-reactor process rather than physical blending. A polypropylene impactcopolymer may contain ethylene comonomer at the amount of at least 5 wt%, or at least 10 wt %; and up to 40 wt %, up to 35 wt %, up to 25 wt %,up to 20 wt %, or up to 15 wt %. Examples of some suitable impactpolypropylene copolymers may be found in U.S. Pat. No. 6,593,005, whichis incorporated herein by reference in its entirety.

The polyolefin base polymer (a) can also be a polymer blend containingethylene propylene rubber (EPR). The term “blend” or “polymer blend”generally refers to a mixture of two or more polymers. Such a blend mayor may not be miscible, and may or may not be phase separated. A polymerblend may or may not contain one or more domain configurations, asdetermined from transmission electron spectroscopy, light scattering,x-ray scattering, or other methods known in the art.

The Coupling Agent (b)

Polymeric Coupling Agent

A coupling reaction refers to a reaction of a polymer with a suitablecoupling agent. The coupling agent used herein comprises a modifiedpolyolefin containing a reactive coupling group at one or more terminalends of the linear or branched chain, hereby referred to as “polymericcoupling agent.” The amount of the polymeric coupling agent used in thecoupling reaction depends on the degree of long-chain branches and themelt strength desired in the resulting long-chain branched polymer orthe amount required to disrupt the surface energy of the final polymerproduct. For instance, the amount of the polymeric coupling agent can beless than 0.01 wt %, less than 0.05 wt %, less than 0.1 wt %, less than0.5 wt %, less than 1 wt %, less than 2 wt %, less than 3 wt %, or lessthan 6 wt %.

Any polyolefin may be used to prepare the modified polyolefin of thepolymeric coupling agent. Suitable modified polyolefins include polymershaving a number average molecular weight of less than 20,000 g/mol, lessthan 15,000 g/mol, or less than 10,000 g/mol, e.g., polyolefins preparedfrom linear or branched olefins having 2 to 20 carbon atoms, 2 to 16carbon atoms, or 2 to 12 carbon atoms, including but not limited toethylene; propylene; 1-butene; 2-butene; 1,3-butadiene; 1-pentene;1,3-pentadiene, 1,4-pentadiene; 3-methyl-1-butene;3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene; 1-hexene;1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene; 4-methyl-1-pentene;3-methyl-1-pentene; 3-methyl-1,5-hexadiene; 3,4-dimethyl-1,5-hexadiene;4,6-dimethyl-1-heptene; 1,3-heptadiene; 1,4-heptadiene; 1,5-heptadiene;1,6-heptadiene; 1-octene; 1,3-octadiene; 1,4-octadiene; 1,5-octadiene;1,6-octadiene; 1,7-octadiene; 1-decene; 1-undecene; 1-dodecene;1-tetradecene; 1-hexadecene; 1-octadecene; 1-eicocene; and combinationsthereof. The polyolefin for preparing the polymeric coupling agent maybe a homopolymer synthesized from a single olefin, or a copolymersynthesized from two or more olefins. For instance, the polyolefin forpreparing the polymeric coupling agent may be polyethylene;polypropylene; copolymers of ethylene and propylene; or terpolymers ofethylene and propylene, and any one of butene, polybutene,polyisobutylene, polybutadiene, and polymethylpentene.

The polymeric coupling agent can have more than one reactive couplinggroups. The reactive coupling group can be the same or different at eachterminal end of the modified polyolefin chain.

The polymeric coupling agent may be prepared by any method known to oneskilled in the art. For instance, the polymeric coupling agentvinyl-polyethylene-N₃ (VPN) used in Examples 1-9 can be prepared byreacting vinyl-polyethylene-I (VPI) with sodium azide. More descriptionsrelating to methods for preparation of telechelic or di-end-functionalpolyethylene may be found in WO 2013/135314; EP 1666507B1; Franssen etal., “Synthesis of functional ‘polyolefins’: state of the art andremaining challenges,” Chem. Soc. Rev. 42, 5809-32 (2013); Yanjarappa etal., “Recent developments in the synthesis of functional poly(olefin)s,”Prog. Polym. Sci. 27: 1347-98 (2002); and Jayaraman et al., “Epoxy andHydroxy Functional Polyolefin Macromonomers,” J. Polym. Sci: Part A:Polym. Chem. 34: 1543-52 (1996); all of which are hereby incorporated byreference in their entirety.

The reactive coupling group is capable of insertion reactions into C—Hbonds of polymers. The C—H insertion reactions and the reactive couplinggroups capable of such reactions are known to one skilled in the art.For instance, the reactive coupling group can be a diazo compound thatgenerates carbene, which is capable of insertion reactions. As anotherexample, the reactive coupling group can contain an azide bond. Thecleavage of the azide bond generates nitrenes (i.e., a nitrogencontaining a sextet of electrons), which is capable of insertionreactions. A further description of nitrene formations can be found inAbramovitch et al., “Thermal decomposition of o- and p-benzenedisulfonylazides in benzene, cyclohexane, cyclohexene, and tetracyclone,” J. Org.Chem. 40(7): 883-889 (1975), which is incorporated herein by referencein its entirety.

The reactive coupling group may also be capable of generating freeradicals that undergo free radical reactions via a radical mechanism tocouple coupling agent (b) with the base polymer, polyolefin (a).Alternatively, the polymeric coupling agent self-couples to form aself-coupled coupling agent and then couples with the base polymer. Asone skilled in the art will understand, the overall reaction can be acombination of these reactions.

The reactive coupling group residing at one or more terminal ends of themodified polyolefin chain can be a same group or a different group. Inone example, the reactive coupling group residing at one or moreterminal ends of the modified polyolefin chain can be an azide group.For instance, when the modified polyolefin chain contains one reactivecoupling group at one terminal end, the reactive coupling group can bean azide group (e.g., azide, an alkyl azide, an aryl sulfonyl azide, aphosphoryl azide, etc.). The modified polyolefin chain can also havereactive coupling groups at two or more terminal ends, or at allterminal ends, and the reactive coupling groups at these terminal endscan each be an azide group. Alternatively, the reactive coupling groupat one terminal end of the modified polyolefin chain is an azide group,and the other terminal ends can contain one or more different reactivecoupling groups (e.g., the reactive coupling group at one terminal endis azide, and the other terminal ends contain a reactive coupling groupdifferent than azide, such as an aryl sulfonyl azide, an alkyl azide,and/or a phosphoryl azide) or non-reactive functional groups.Non-reactive functional groups, for the purpose of this invention, arenon-reactive with the base polymer, polyolefin (a), or with thepolymeric coupling agent itself, but can be reactive to other groups ormaterials, such as inorganic materials.

Accordingly, suitable terminal groups of the modified polyolefin chainfor the polymeric coupling agent include reactive coupling groups and/ornon-reactive functional groups. Exemplary reactive coupling group ornon-reactive functional groups include, but are not limited to,peroxides, alkyl boranes, halogens, thiols, amines, amides, aldehydes,alcohols, carboxylic acids, esters, diazo, isocyanates, silanes,phosphorous-containing groups, dithioesters, dithiocarbamates,dithiocarbonates, trithiocarbonates, alkoxyamines, aryl sulfonyl groups(such as aryl sulfonyl halides or aryl sulfonyl azides), phosphorylazides, vinyls (such as vinyl, alkyl vinyls, vinylidenes, or arylvinyls), dienes, dyes, porphyrins, alkyl azides, or derivatives thereof.For instance, the terminal group of the polymeric coupling agent can bean alkyl vinyl group.

In certain embodiments, the polymeric coupling agent has the structureof Formula I:R

X

_(n)R′—N₃  (I)

R is a peroxide, alkyl borane, halogen, thiol, amine, amide, aldehyde,alcohol, carboxylic acid, ester, isocyanate, silane,phosphorous-containing group, dithioester, dithiocarbamate,dithiocarbonate, trithiocarbonate, alkoxyamine, aryl sulfonyl halide,aryl sulfonyl azide, phosphoryl azides, vinyl (e.g., vinyl, an alkylvinyl, vinylidene, or aryl vinyl), diene, porphyrin, dye, alkyl azide,or a derivative thereof.

(X)_(n) is a polyolefin radical. X is a monomeric olefin unit that islinear or branched, saturated or unsaturated, and contains 2 to 10carbon atoms. If branched, the branches may contain cyclic saturated,cyclic unsaturated, aromatic, saturated linear, or unsaturated linearhydrocarbyl group(s); the branches may or may not contain heteroatomssuch as fluorine, chlorine, bromine, iodine, oxygen, sulfur, selenium,nitrogen, phosphorous, silicon, and boron. The integer n is at least 2,at least 5, or at least 10. For instance, n is 2 to 1000, 2 to 500, 5 to500, 10 to 500, 10 to 200, 10 to 100, or 10 to 50.

R′ is methylene, aryl, aryl sulfonate, oxy aryl sulfonate, acrylate,aryl acyl, alkyl acyl, epoxy, ester, amine, amide, diazo, orcombinations thereof.

Molecular Coupling Agent

One or more molecular coupling agents can be blended with the polymericcoupling agent. If the polymeric coupling agents have relatively highthermal stability, a molecular coupling agent may be used to promote thecoupling reaction between the polyolefin base polymer (a) and thepolymeric coupling agent. For instance, these molecular coupling agentscan be added to promote the coupling reaction by generating radicals ata lower temperature thereby promoting the coupling reaction.

Exemplary molecular coupling agents include peroxides, such asdi(4tert-butylcyclohexyl) peroxydicarbonate,di(tert-butylperoxyisopropyl)benzene,di(tert-butylperoxyisopropyl)benzene, di(4-methylbenzoyl) peroxide,dicetyl peroxydicarbonate, dimyristyl peroxydicarbonate, dicumylperoxide, dibenzoyl peroxide, diisopropyl peroxydicarbonate, tert-butylmonoperoxymaleate, didecanoyl peroxide, dioctanoyl peroxide,2,5-dimethyl-2,5-di(tert-butylperoxy) hexane,tert-butylperoxy-2-ethylhexyl carbonate, tert-amylperoxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, tert-amylperoxypivalate, tert-amyl peroxybenzoate, tert-amyl peroxyacetate,di-sec-butyl peroxydicarbonate, di(2-ethylhexyl) peroxydicarbonate,tert-butyl cumyl peroxide or combinations of these non-limitingexamples; an alkyl borane, such as triethylborane, trimethylborane,tri-n-butylborane, triisobutylborane, diethylborane methoxide, ordiethylborane isopropoxide or combinations of these non-limitingexamples; azo compounds such as azobisisobutyronitrile (AIBN) or1,1′-azobis(cyclohexanecarbonitrile) (ABCN),1,1′-azodi(hexahydrobenzonitrile, 2,2′-Azodi(hexahydrobenzonitrile,2,2′-azodi(2-methylbuttyronitrile, or combinations of these non-limitingexamples; azide compounds such as 4,4′-oxybis(benzenesulfonyl azide),4-dodecylbenzensulfonyl azide, benzenesulfonyl azide,4-(2-trimethoxysilylethyl) benzenesulfonyl azide,4-methylbenzenesulfonyl azide, 2,4,6-triisopropylbenzenesulfonyl azide,1,3-benzenedisulfonyl azide, 1,4-benzenedisulfonyl azide; orcombinations of these non-limiting examples.

An exemplary polymeric coupling agent contains VPN.

An exemplary coupling agent is a blend of a polymeric coupling agentcontaining VPN and a molecular coupling agent containing4,4′-oxybis(benzenesulfonyl azide).

Another exemplary coupling agent is a blend of a polymeric couplingagent containing VPN and a molecular coupling agent containingdi(4tert-butylcyclohexyl) peroxydicarbonate.

The above-described polymeric coupling agent and polymeric/molecularcoupling agent blend are different than a coupling agent based onmolecular aryl azides or sulfonyl azides, such as4,4′-oxybis(benzenesulfonyl azide), used in a blend with an inertadditive (e.g., Irganox 1010). By using a polymeric coupling agenthaving azide group at one or more terminal ends of the modifiedpolyolefin, various aspects over using a molecular coupling agent can beimproved, from the process to the final product.

For instance, when preparing a long-chain branched polypropylene using4,4′-oxybis(benzenesulfonyl azide) as a coupling agent, the processtypically involves the preparation of a blend of the4,4′-oxybis(benzenesulfonyl azide) with an inert additive (e.g., Irganox1010), which aims to dilute the molecular azide compound to avoid rapiddecomposition. To activate 4,4′-oxybis(benzenesulfonyl azide) blendedwith the inert additive, the extrusion reactive conditions typicallyinvolve heating to 230° C. and having the molecular coupling agent(i.e., 4,4′-oxybis(benzenesulfonyl azide) at a concentration of at least1625 ppm (1.6g/kg of polypropylene). However, the polymeric couplingagent containing an azide group at one or more terminal ends of themodified polyolefin described in this invention, does not need to bedispersed in an inert medium, such as the anti-oxidant PentaerythritolTetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate). Thus, thecoupling reaction between the polyolefin base polymer (a) and thepolymeric coupling agent can take place without the presence of an inertcomponent.

Employing 4,4′-oxybis(benzenesulfonyl azide) as a molecular couplingagent promotes a shorter linkage, whereas a polymeric coupling agenthaving an azide group at one or more terminal ends of the polymericcoupling agent chain may promote the formation of a longer linkagebetween two base polyolefin chains. Employing a polymeric coupling agentcontaining azide groups at all terminal ends may also promote theformation of a crosslinked or hyperbranched structure in the resultinglong-chain branched polymer.

The relatively higher thermal stability of the polymeric coupling agent,as compared to the molecular coupling agent (e.g.,4,4′-oxybis(benzenesulfonyl azide)), provides an improved performanceand safety in the handling process. Thus, the polymeric coupling agentcan be handled as a normal polyolefin powder, rather than beingdispersed in an inert matrix. For instance, as discussed in Example 1,VPN samples are stable at temperatures below 190° C., which is safe forhandling and storage at industrial scales.

Moreover, alkyl azides, such as a polymeric coupling agent having anazide group at one or more terminal ends, tend not to form HN₃ duringthe coupling reaction. This is a notable improvement, especiallycompared to 4,4′-oxybis(benzenesulfonyl azide), which containselectrophilic sulfonyl groups which is more likely than alkyl azides torelease HN₃ in presence of moisture during the coupling reaction.

Additionally, using a polymeric coupling agent having an azide group atone or more terminal ends shows a better compatibility with the basepolymer, avoiding blooming issues—migration of the additive to thepolymer surface—which may occur when using blends of4,4′-oxybis(benzenesulfonyl azide) and inert materials (e.g.,PentaerythritolTetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)).

Reaction Conditions

The reaction temperature of the coupling reaction between the polyolefinbase polymer (a) the coupling agent (b) (containing polymeric couplingagent or polymeric/molecular coupling agent blend) can be greater than140° C., or greater than 220° C. Typically, the coupling reaction occursat or above the first decomposition temperature of the polymericcoupling agent or the polymeric/molecular coupling agent blend, but lessthan 350° C. For instance, the first decomposition temperature of thepolymeric coupling agent, such as VPN, is 190° C. or higher. On theother hand, a polymeric/molecular coupling agent blend can have adecomposition temperature of 140° C. or higher. The decompositiontemperature may be determined by Thermal Gravimetric Analysis (TGA) orother means known to one skilled in the art. TGA measurements andthermogram of the exemplary polymeric coupling agent andpolymeric/molecular coupling agent blends, are provided in Examples 1-6,in which the decomposition curves were analyzed and displayed in FIGS. 3and 8, and Table 1.

The azide-containing modified polyolefin can decompose in several ways.(The process of the invention is not intended to be bound by differentreaction mechanisms.) As an example, insertion of the azide-containingpolymeric coupling agent into a polyolefin base polymer (a) generallyoccurs through the thermal decomposition of the azide group. At or abovethe first decomposition temperature of the azide-containing polymericcoupling agent or the first decomposition temperature of thepolymeric/molecular coupling agent blend, the polymeric coupling agentgenerates nitrene species (aza derivatives), acting as an efficientcoupling agent to react with the polyolefin base polymer (a). See, e.g.,the reaction scheme in Scheme 1.

Advantageously, at or above the first decomposition temperature of theazide-containing polymeric coupling agent or the first decompositiontemperature of the polymeric/molecular coupling agent blend, theazide-containing polymeric coupling agent is capable of a self-couplingreaction (in the polymeric coupling agent or the polymeric/molecularcoupling agent blend), in which the formed azo radical groups reactswith other polymeric coupling agent chains. Thus, in certainembodiments, the polymeric coupling agent self-couples to form aself-coupled coupling agent capable of reacting with the polyolefin basepolymer (a).

The polyolefin base polymer (a) and the coupling agent (b) can beadmixed, or otherwise combined, under conditions which allow forsufficient mixing before or during the coupling reaction. Admixing ofthe polyolefin base polymer (a) the coupling agent (b) can beaccomplished by any means known to one skilled in the art. During theadmixing/combining, it is desirable to have as homogeneous adistribution as possible, to achieve solubility of the coupling agent inthe polyolefin melt, and to avoid uneven amounts of localized reactions.The resulting admixture can be subjected to heating step to initiate thereaction.

For example, the coupling reaction can occur by subjecting thepolyolefin base polymer (a) the coupling agent (b) to a melt process toblend the polyolefin and coupling agent to achieve the reaction. Theterm “melt processing” is used to mean any process in which polymers,such as the polyolefin base polymer (a) or the coupling agent (b), aremelted. Melt processing includes extrusion, pelletization, film blowingor casting, thermoforming, compounding in polymer melt form, fiberspinning, or other melt processes.

Any equipment suitable for a melt processing can be used as long as itprovides sufficient mixing and temperature control. For instance, acontinuous polymer processing system such as an extruder, a staticpolymer mixing device such as a Brabender blender, or a semi-continuouspolymer processing system, such as a BANBURY mixer, can be used. Theterm “extruder” is used for its broadest meaning, to include any machinefor polyolefin extrusion. For instance, the machine can extrudepolyolefin in the form of powder or pellets, sheets, fibers, or otherdesired shapes and/or profiles. Generally, an extruder operates byfeeding material through the feed throat (an opening near the rear ofthe barrel) which comes into contact with one or more screws. Therotating screw(s) (normally turning at up to 120 rpm) forces thepolyolefin forward into one or more heated barrels (e.g., there may beone screw per barrel). In many processes, a heating profile can be setfor the barrel in which three or more independentproportional-integral-derivative controller (PID)-controlled heaterzones can gradually increase the temperature of the barrel from the rear(where the plastic enters) to the front.

The process of the invention can take place in a single-vessel, i.e.,the mixing of the polyolefin base polymer (a) the coupling agent (b)takes place in the same vessel that heats the mixture to thedecomposition temperature of the coupling agent(s). It can be, forinstance, a single-screw or a twin-screw extruder, or a batch mixer.Further descriptions about extruders and processes for extrusion can befound in U.S. Pat. Nos. 4,814,135; 4,857,600; 5,076,988; and 5,153,382;all of which are incorporated herein by reference.

The reaction vessel can have more than one zone of differenttemperatures into which a reaction mixture would pass: the first zonecan be at a temperature of at least the crystalline melt temperature orthe softening temperature of the polyolefin base polymer(s) (a) and thesecond zone can be at a temperature sufficient for the decomposition ofthe coupling agent (b). It is desirable that the first zone is at atemperature of less than the decomposition temperature of the couplingagent, but sufficiently high to soften the polyolefin and allow it tocombine with the coupling agents (b) through distributive mixing to asubstantially uniform admixture.

When a melt extrusion is used, the reaction can take place during themelt extrusion step. The heat produced during the extrusion stepprovides the energy necessary to cause the reaction between the couplingagents (b) with the polyolefin base polymer (a). A temperature at orabove the decomposition temperature of the coupling agents (b) may bemaintained for a time sufficient to result in decomposition of thecoupling agent so that at least 50 wt %, at least 60 wt %, at least 70wt %, at least 80 wt %, at least 90 wt %, or at least 95 wt % of thecoupling agent is reacted. For instance, the residence time may be atleast 1 second, at least 3 seconds, at least 5 seconds, at least 10seconds, or at least 15 seconds, to avoid unreacted coupling agent, andsubsequent undesirable reactions, or to avoid the need for possibledestructively high temperatures. Typically, the reaction time is 15-90seconds.

One skilled in the art understands that a polyolefin or mixtures thereoftypically melts over a temperature range rather than sharply at onetemperature. Thus, it may be sufficient that the polyolefin be in apartially molten state. The melting or softening temperature ranges canbe approximated from the differential scanning calorimeter (DSC) curveof the polyolefin or mixtures thereof.

Improved incorporation of the coupling agents (b) can be achieved byblending a solution or fluid form of the coupling agents (b) into thepolyolefin phase, to allow the polyolefin to blend the coupling agents(b). If there is solvent in the mixture, solvent is evaporated and theresulting mixture is extruded. The solvents used can be polar solventssuch as acetone, THF (tetrahydrofuran), or non-polar compounds such asmineral oils, toluene, hexane, heptane, cyclohexane, benzene, and otherhydrocarbons which the coupling agent is sufficiently miscible todisperse the coupling agent in a polyolefin.

Alternatively, the coupling reaction between the polyolefin base polymer(a) and the coupling agent (b) can take place under solventless reactionconditions. The coupling reaction can be carried out in a bulk phase, toavoid later steps for removal of the solvent or other medium.

Alternatively, the coupling agents (b) can be added to the post-reactorarea of a polymer processing plant, to avoid the extra step ofre-extrusion and the cost associated with it and to ensure that thecoupling agents (b) are well blended into the polyolefin base polymer.For instance, after the polyolefin is produced in a slurry process, thecoupling agents (b) can be added in powder or liquid form to thepowdered polyolefin after the solvent is removed by decantation andprior to the drying and densification extrusion process. In analternative embodiment, when a polyolefin is prepared in a gas phaseprocess, the coupling agents (b) can be added in powder or liquid formto the powdered polyolefin before the densification extrusion. In analternative embodiment, when a polyolefin is made in a solution process,the coupling agent (b) can be added to the polyolefin solution prior tothe densification extrusion process.

The kinetics of the coupling reaction depend upon the molecularstructure of the coupling agent (e.g., whether one terminal end or allterminal ends contains reactive coupling groups or the chemicalcomposition of the azide groups), whether a molecular coupling agent(e.g., peroxides and/or azides) is added/blended to the polymericcoupling agent, the processing conditions (the temperature of thereaction system, the type of reaction vessels, and residence times,etc.), and other variables appreciated by one skilled in the art.

Long-Chain Branched Polymers

Another aspect of the invention relates to a long-chain branched polymerprepared according to the processes as discussed in the aboveembodiments. The long-chain branched polymer is formed by reacting (a) apolyolefin base polymer with (b) coupling agent comprising a polymericcoupling agent, optionally blended with a molecular coupling agent, thepolymeric coupling agent being a modified polyolefin having a reactivecoupling group at one or more terminal ends of the modified polyolefinchain, to couple the polyolefin base polymer (a) with the coupling agent(b). Suitable polyolefin base polymers (a), polymeric coupling agent andpolymeric/molecular coupling agent blends, reactive coupling groups, andnon-reactive functional groups (i.e., non-reactive with the basepolyolefin and with the polymeric coupling agent itself, but can bereactive to other groups or materials, such as inorganic materials), aswell as suitable coupling reaction conditions for preparing theselong-chain branched polymers are the same as those descriptions relatingto the process as discussed in the above embodiments. The resultinglong-chain branched polymer depends upon the starting materials andreaction conditions used.

In one embodiment, one or more terminal ends of the modified polyolefinchain contains a reactive coupling group or non-reactive functionalgroup (e.g., R in formula (I)) selected from the group consisting ofperoxides, alkyl boranes, halogens, thiols, amines, amides, aldehydes,alcohols, carboxylic acids, esters, isocyanates, silanes,phosphorous-containing groups, dithioesters, dithiocarbamates,dithiocarbonates, trithiocarbonates, alkoxyamines, aryl sulfonylhalides, aryl sulfonyl azides, vinyl, dienes, porphyrins, dyes, alkylazides or derivatives thereof.

The polyolefin base polymer (a) can contain one or more binding sitesalong the polyolefin chain. Accordingly, in the resulting long-chainbranched polymer, one or more modified polyolefins of the polymericcoupling agent or the polymeric/molecular coupling agent blend may becovalently bonded at one or more binding sites along the chain of thepolyolefin base polymer (a).

As discussed above, the modified polyolefin of the polymeric couplingagent or the polymeric/molecular coupling agent blend can self-couple toform a self-coupled coupling agent (i.e., each polymeric coupling agentcan couple with each other to form a longer coupling agent containingone or more modified polyolefin chains). This self-coupled couplingagent, when covalently bonded to the polyolefin base polymer chain, canintroduce elongated long-chain branches into the polyolefin basepolymer. Thus, in the resulting long-chain branched polymer, one or morebinding sites along the chain of the base polymer, polyolefin (a), cancontain a long-chain branch that covalently links one or more modifiedpolyolefin chains.

Accordingly, in certain embodiments, the resulting long-chain branchedpolymer contains branched chains resulting from both the reaction of thepolyolefin base polymer (a) with the coupling agent, and the reaction ofthe polyolefin base polymer (a) with the self-coupled polymeric couplingagent. The resulting long-chain branched polymer may be a cross-linkedor a hyperbranched polyolefin, based on the distribution of the reactivegroups on the polymeric coupling agent (or polymeric/molecular couplingagent blend), and the self-coupling reaction of the polymeric couplingagent (or polymeric/molecular coupling agent blend).

Another aspect of the invention relates to a long-chain branchedpolymer, comprising a polyolefin base polymer that contains one or morelong-chain branches formed by covalently bonding one or more polymericcoupling agents at one or more binding sites along the polyolefin basepolymer chain.

The polymeric coupling agents can be a modified polyolefin having areactive coupling group at one or more terminal ends of the modifiedpolyolefin chain, prior to covalently bonding to the polyolefin basepolymer.

Suitable polyolefin base polymers (a), polymeric coupling agents (orpolymeric/molecular coupling agent blends) are the same as thosediscussed in the above embodiments.

In certain embodiments, in the long-chain branched polymer, at least onelong-chain branch along the base polyolefin chain is formed byself-coupling two or more polymeric coupling agents. Thus, one or morelong-chain branches introduced into one or more binding sites along thepolyolefin base polymer chain can contain two or more polyolefinscovalently bonded together through self-coupling the two or morepolymeric coupling agents. The resulting long-chain branched polymer maycontain crosslinked structures, which, may varies on the degree ofcrosslinking.

As the result of introducing a high degree of long-chain branches intopolyolefins, the melt strength of the resulting long-chain branchedpolymer can be advantageously increased by the coupling reaction, asdiscussed in the above embodiments. The melt strength can be determinedfrom (R_(g) ²)^(1/2) (R_(g), radius of gyration) and intrinsic viscosity[η] measured by size-exclusion chromatography (SEC) equipped with lightscattering or viscosity detector, respectively. As a result of theformation of long-chain branches, the polymer becomes more compact insolution and the R_(g) values decrease and η values increase byincreasing the number of branches. Thus, the decreased values of R_(g)and the increased values of η relative to the base polyolefin resinwould indicate the formation of long-chain branches in the polymer. Inthis case, the number of branch points per molecule for the resultinglong-chain branched polymer should be higher than zero. A melt tensiletechnique, such as Rheotens experiment, can also be used to indicate theresult of melt strength of the polymer. Typically, values higher than0.1N can be assigned to the formation of long-chain branchedpolypropylene, since force (F) is relative to the melt strength of thepolymer.

Heterophasic Blend

The resulting long-chain branched polymer from the above-describedprocesses can be further blended with a second polyolefin that is in adifferent phase than the long-chain branched polymer. This can result ina modified impact copolymer. In an automotive application (such asautomotive parts like bumpers, body panels, dashboards, or doorcladdings), it is desirable to have a heterophasic blend of polymers,i.e., a polymer in a continuous phase and a polymer in a elastomeric,dispersed phase are blended. For instance, a blend of apolypropylene-based polymer (e.g., homopolymer polypropylene) and anethylene-propylene copolymer (EPR) is a heterophasic blend, in which thepolypropylene-based polymer is the continuous phase and the EPR is thedispersed phase. The polypropylene-based matrix delivers the stiffnessof the material whereas the rubbery inclusions act as impact modifiersproviding a grade with balanced stiffness-impact behavior. In oneembodiment, the long-chain branched polymer is prepared frompolypropylene as the base polyolefin (a), and can be used as acontinuous phase of a heterophasic polymer blend. This long-chainbranched polypropylene-based polymer is further blended with a secondpolyolefin that is in a different phase (i.e., elastomeric, dispersedphase) such as an EPR, to prepare a modified impact copolymer.

Uses of the Long-Chain Branched Polymer

The long-chain branched polymer prepared according to the processes ofthe invention may be formed into useful articles by standard formingmethods known in the art, e.g., by blown film extrusion, cast filmextrusion, injection or blow molding, pelletizing, foaming,thermoforming, compounding in polymer melt form, or fiber spinning. Forexample, any technique discussed above in the embodiments describing themelt processes can be used to prepare the long-chain branched polymer,thereby forming various useful articles, depending on the type of meltprocessing technique used.

For instance, the long-chain branched polymer may be useful in makingfilms, such as blown films. The technique of blown film extrusion isknown to one skilled in the art in the area of production of thinplastic films.

The long-chain branched polymer may also be used in coextruded films.The formation of coextruded blown films is known to one skilled in theart. The term “coextrusion” refers to the process of extruding two ormore materials through a single die with two or more orifices arrangedsuch that the extrudates merge together into a laminar structure, forinstance, before chilling or quenching.

Coextruded blown films containing the long-chain branched polymer can beformed into pouches, bags, containers using packaging machinery known toone skilled in the art. Pouches, bags and other containers made fromthis combination of materials provide excellent toughness and impactstrength and furthermore provide an excellent barrier to grease and oiland light hydrocarbons such as turpentine.

The long-chain branched polymer can also be useful in fabricating moldedarticles and fiber articles; in fabricating foams, wire cable, andprofile extrusion; and in automotive applications, such as automotiveparts like bumpers, body panels, dashboards, or door claddings.

Functionalization of Polyolefins and Compatibility with InorganicMaterials

The coupling reaction can also be used to functionalize a polyolefinusing a modified polyolefin as a building block, and/or improve thecompatibility of the polyolefin with inorganic materials. A polymericcoupling agent may have reactive coupling groups at one or more terminalends of the modified polyolefin chain and one or more differentnon-reactive functional groups that are non-reactive with the polyolefinbase polymer (a) and with the polymeric coupling agent itself. Suitablepolymeric coupling agents and their reactive and non-reactive terminalgroups are the same as those descriptions relating to the process asdiscussed in the above embodiments. One purpose of introducing anon-reactive functional group that does not react with the basepolyolefin polymer or with the polymeric coupling agent is to improvethe compatibility between the base polyolefin polymer and inorganicmaterial for composite formation and improve the interaction between thebase polyolefin polymer and inks/pigments for paintability.

Functionalizing polyolefins can be carried out by incorporation of bulkypolar groups via a reaction with the reactive coupling group on one ormore terminal ends of the polymeric coupling agent chain. The presenceof the non-reactive functional group (i.e, non-reactive with the basepolyolefin and with the polymeric coupling agent itself, but can bereactive to other groups or materials, such as inorganic materials) inat least one end of the polymer chain may disrupt surface energy of thefinal product after the coupling reaction, thereby improving thepaintability, surface adhesion, compatibility with inorganic materials,and ultimately resulting in a functionalized polyolefin.

As noted above, the non-reactive functional group is non-reactive withthe base polyolefin and with the polymeric coupling agent itself, butcan be reactive to other groups or materials, such as inorganicmaterials. For example, during a reactive extrusion experiments, thestarting materials can be a base polyolefin and a polymeric couplingagent comprised of an reactive group, such as azide, and a non-reactivefunctional group, such as maleic anhydride, at each end, respectively.The azide group would react with the base polyolefin polymer but themaleic anhydride group would not react with the base polyolefin polymer.In another experiment, the starting materials can be a base polyolefinpolymer, the same polymeric coupling agent, and silica particles. Inthis experiment, the azide group reacts with the base polyolefinpolymer, and the maleic anhydride group reacts with the hydroxyl groupson the surface of the silica particles. In the first example above, themaleic anhydride group acts as a modifier of the surface energy of thepolymer, because this polar group would migrate to the surface of thepolymer while one end is covalently bonded to the base polymer, whichwould increase the paintability. In the second example above, the maleicanhydride group improves the compatibility of the base polymer with aninorganic particle, which may also disrupt the surface energy due toinherent incompatibility of these two materials.

Accordingly, the process of the invention can further comprise the stepof adding an inorganic material containing a polar group during thecoupling reaction between the polyolefin base polymer (a) with thecoupling agent (b) that includes a modified polyolefin.

Any inorganic material containing a polar group and capable of reactingwith the coupling agent can be used. Suitable inorganic materialsinclude, but are not limited to, glass fibers, inorganic fibers,functionalized silica nanoparticles, polyhedral oligomericsilsesquioxane (POSS), dyes, functionalized carbon nanotubes, clay, andcombinations thereof.

Alternatively, another aspect of the invention relates to a process forpreparing a composite containing a polyolefin and an inorganic material.The process comprises reacting (i) a polymeric coupling agent with (ii)an inorganic material containing a polar group and capable of reactingwith the polymeric coupling agent to form a composite containing thepolymeric coupling agent and inorganic material.

Suitable polymeric coupling agents and inorganic materials, as well assuitable coupling reaction conditions and reaction equipment are thesame as those descriptions relating to the process as discussed in theabove embodiments.

Another aspect of the invention relates to a composite containing apolyolefin and an inorganic material. The composite is preparedaccording to the process comprising the step of reacting (i) polymericcoupling agent with (ii) an inorganic material containing a polar groupand capable of reacting with the polymeric coupling agent.

Suitable polymeric coupling agents and inorganic materials, as well assuitable coupling reaction conditions and reaction equipment are thesame as those descriptions relating to the process as discussed in theabove embodiments. The resulting composite depends upon the startingmaterials and reaction conditions used.

The inorganic material can contain multiple polar groups and hencemultiple reactive sites. Accordingly, one or more modified polyolefinchains can be covalently bonded at one or more binding sites of theinorganic material.

As discussed above, the modified polyolefin can self-couple to form aself-coupled coupling agent containing one or more polymeric couplingagent chains. Thus, in the resulting composite, one or more reactivesites in the inorganic material can contain a long-chain branch thatcovalently links one or more modified polyolefin chains.

Accordingly, in certain embodiments, the resulting composite containsbranched chains resulting from both the reaction of the polymericcoupling agent (i) with the inorganic material (ii), and the reaction ofthe modified polyolefin with itself.

EXAMPLES

The following examples are for illustrative purposes only and are notintended to limit, in any way, the scope of the present invention.

Example 1 VPN as a Polymeric Coupling Agent and Self-Coupling Reactions

VPN was prepared from VPI as the starting material and the referencematerial as a polymeric non-coupling agent. Because of the substitutionreaction of the iodine group to the azide group, the two polymers havesimilar molecular weight, similar molecular weight distribution, withthe same main chain. The two polymers differ only on the functionalgroup at one end of the polymer chain, as showing in the ¹H NMR spectrain FIG. 1. The presence of the azide group was also confirmed by FTIR asshown in FIG. 2.

The molecular weights of the polymeric non-coupling agent (VPI) and thepolymeric coupling agent (VPN) were estimated by size-exclusionchromatography (SEC), and the results displayed in FIG. 5 shows ananalogous molecular weight (MW) and molecular weight distribution (MWD)between VPI and VPN.

As shown in FIG. 3, the thermogravimetric analysis (TGA) showed a firstdecomposition curve for the polymeric coupling agent VPN starting atapproximately 190° C. of roughly 4 wt % of weight loss, which isassigned to the N₂ loss due to the formation of the nitrene radical, asrepresented in Scheme 1. Such behavior was not observed in a polymericnon-coupling agent such as VPI.

In FIG. 4, the DSC thermograms show the presence of two distinctendotherm peaks in the VPN sample, suggesting the presence of differentcrystal sizes and lattice structures. The formation of the self-coupledmaterial resulted in an increase of about 5° C. of the maincrystallization temperature peak (at approximately 95° C. and 100° C.,respectively; see a more clear view of the two peaks in the enlargedwindow A) and the sharpening of the endothermic peak after the secondscan during the DSC analysis. Furthermore, during the first DSC scan, anexothermic curve was observed at approximately 170° C., which suggeststhe formation of nitrene species and a resulting self-coupling reaction.

In addition to the DSC analysis, the self-coupled VPN sample wascharacterized by SEC and compared with the VPI and VPN samples, as shownin FIG. 5. A formation of a high molecular weight shoulder was observedin the self-coupled VPN sample as a result of the self-coupling reactionbetween the coupling group (azide group) and the polymer main chainwithin the polymeric coupling agent VPN. This result converges with theresults obtained by the thermal analysis, i.e., for the VPN sample, theTGA results showed that the first decomposition analysis showed a weightloss of approximately 4 wt % followed by an increase of the T_(20%)(T_(20%) corresponds to the temperature of 20% of weight loss) ofapproximately 43° C., as shown in Table 1, due to the increase of themolecular weight after the self-coupling reactions of the polymericcoupling agent VPN.

Other relevant information obtained from ¹³C NMR spectra, shown in FIG.6, reveals that the vinyl group did not react after the polymericcoupling agent VPN sample was recovered from the DSC analysis.Furthermore, a down field shift was observed for C(1), suggesting aneffective coupling insertion of the azide group into the polymer mainchain. Therefore, the results show that the VPN sample may generate thenitrene species at temperature above 180-190° C. Additionally, it showsthat the singlet nitrene will undergo to a coupling reaction with theC—H bonds of the polyethylene section of the polymeric coupling agentVPN, producing a high molecular weight self-coupled polymer, which maybe grafted or hyper-branched.

TABLE 1 T_(20%) and T_(onset) results for polymeric coupling agent andpolymeric coupling agent blends in self-coupling reactions PolymericCoupling Agent Molecular Coupling Blend Ratio T_(20%) T_(onset) (PCA)Agent (MCA) code (PCA:MCA) (° C.) (° C.) VPN NONE N/A N/A 424.1 190 VPN4,4′- B1 2:1 N/A N/A oxybis(benzenesulfonyl azide VPN 4,4′- B2 1:1 400.1140 oxybis(benzenesulfonyl azide VPN Bis(tert- B3 10:1  488.4 140butylcyclohexyl) peroxydicarbonate VPN Bis(tert- B4 1:1 N/A N/Abutylcyclohexyl) peroxydicarbonate

Example 2 Preparation of VPN and 4,4′-oxybis(benzenesulfonyl azide) asPolymeric/Molecular Coupling Agent Blend, Blend B1

After recovering the produced VPN (polymeric coupling agent), 41.3 g ofthe VPN sample was dispersed in 0.6L of toluene at 40° C. and themixture was stirred until the entire polymer sample is swollen. Then, asolution of 34.45 g of the molecular coupling agent4,4′-oxybis(benzenesulfonyl azide):PentaerythritolTetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate) (25:75 wt %)in 0.3L of toluene was added to the system, which enabled to achieve agood dispersion. The resulting mixture was stirred for an additional 30minutes at 40° C. and then cooled down to room temperature, and thesolvent was recovered under reduced pressure to obtain a white solid.The white solid was dried under reduced pressure for approximately 6hours and grinded to obtain a fine white powder of Blend B1 at a molarratio of 2:1 polymeric coupling agent:molecular coupling agent.

FIG. 7 shows the ¹H NMR spectra comparing the spectra of the molecularcoupling agent 4,4′-oxybis(benzenesulfonyl azide) (including thepresence of the anti-oxidant PentaerythritolTetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate)) and the finalBlend B1. It shows that the coupling agents were fully recovered andthere was not observed a side reaction during the preparation of theblend. Scanning Electron Microscopy (SEM) results (not provided) show auniform distribution of the produced blend.

Example 3 Preparation of VPN and 4,4′-oxybis(benzenesulfonyl azide) asPolymeric/Molecular Coupling Agent Blend, Blend B2

Same procedure was used as described for Blend B1 in Example 2, exceptthat the molar ratio of the polymeric coupling agent:molecular couplingagent was 1:1.

Example 4 Preparation of VPN and Bis(tert-butylcyclohexyl)peroxydicarbonate as Polymeric/Molecular Coupling Agent Blend, Blend B3

Same procedure was used as described for Blend B1 in Example 2, exceptthat the molar ratio of the polymeric coupling agent:molecular couplingagent was 10:1.

Example 5 Preparation of VPN and Bis(tert-butylcyclohexyl)peroxydicarbonate as Polymeric/Molecular Coupling Agent Blend, Blend B4

Same procedure was used as described for Blend B1 in Example 2, exceptthat the molecular coupling agent used was bis(tert-butylcyclohexyl)peroxydicarbonate, and the molar ratio of the polymeric couplingagent:molecular coupling agent was 1:1.

Example 6 Polymeric/Molecular Coupling Agent Blends and Self-CouplingReactions

As shown in FIG. 8, the decomposition analyses were carried out by TGAto compare the T_(onset), which is assigned for the first decompositionof the azide group followed by the loss of nitrogen gas, of thepolymeric non-coupling agent VPI (reference), the polymeric couplingagent (VPN), and the polymeric coupling agent blends (B2 and B3). Theresults showed a decrease of approximately 50° C. of the T_(onset),suggesting that the presence of the molecular coupling agent promotedthe decomposition of the azide group. An increase of T_(20%) compared tothe reference was also observed, as a result of the increase of themolecular weight after the self-coupling reactions of the polymericcoupling agent and molecular coupling agent.

Example 7 Polymeric Coupling Agent and Homo-Polypropylene: CouplingReaction (P1)

The coupling reaction between VPN and homo-polypropylene (HPP) of meltflow index of 2.0 dg/min was carried out in a Brabender mixer. In orderto evaluate the shear and temperature effect on the integrity of thefinal polymer after the blending process, a reference sample of HPP wasalso processed in a Brabender mixer under the same conditions. Forinstance, 20 g of the HPP as a base resin was initially added toBrabender mixer and the temperature was kept at 240° C. under nitrogenflow for 45 seconds or until HPP was completely melted. The reaction wasfollowed by the addition of 0.4 g of the polymeric coupling agent VPN(2.0 wt %) under the same conditions and the resulting mixture wasreacted for an additional 120 seconds.

As a result of an efficient coupling reaction between VPN and HPP, anendothermic peak corresponding to the VPN at approximately 105° C. wasnot detected, as shown in FIG. 9. On the other hand, when a non-couplingagent such as VPI was blended with HPP under the same conditions, anendothermic peak at 102° C. was noticeable. This result was the firstindication of the effective reaction between the polymeric couplingagent VPN and the HPP.

Furthermore, the rheology data shown in FIGS. 10 and 11 also support themodification of the HPP sample by the VPN under the condition describedabove. FIG. 10 shows an increase of the complex viscosity and a steepercurve over the HPP sample, indicating a higher degree of entanglement ofthe chain after the reaction between VPN and HPP, suggesting aviscoelastic behavior of the HPP+VPN sample. This was also confirmed inFIG. 11, as the tan δ values of the HPP+VPN sample are lower than theHPP sample, showing a longer relaxation of the sample specially at alower angular frequency.

Example 8 Polymeric Coupling Agent and Homo-Polypropylene: CouplingReaction (P2)

The coupling reaction between VPN and homo-polypropylene (HPP) of meltflow of 2.0 dg/min was carried out in a Brabender mixer. In thisexperiment, 20 g of HPP and 1.0 g of the polymeric coupling agent VPN(5.0 wt %) were added together to the Brabender mixer at 240° C. Thereaction was kept under nitrogen and several samples were collectedbetween 30 seconds and 180 seconds. In order to evaluate the shear andtemperature effect on the integrity of the final polymer after theblending process, a reference sample of HPP was also processed in aBrabender mixer under the same conditions, and the samples of the HPPwere also collected between 30 seconds and 180 seconds.

The results from dynamic shear measurement are shown in FIG. 12. TheHPP+VPN sample started to form a plateau at a lower angular frequencywhich was more pronounced at a longer reaction time. It is a clearevidence of stronger entanglements of the resulting polymer chains afterthe incorporation of the VPN sample. On the other hand, no shearrecovery was observed on the HPP samples showing an enhanced degradationon the sample kept collected even after 180 seconds.

Example 9 Polymeric/Molecular Coupling Agent blends andHomo-Polypropylene: Residual Azide (P3)

The coupling reaction between a homo-polypropylene (HPP) of melt flow of2.0 dg/min was carried out with the polymeric coupling agent at theconditions described in Examples 7 and 8. The polymer product showed thepresence of residual azide groups, which were detected by FTIR as shownin FIG. 13. The samples were collected at approximately 45 seconds (P1a& P2a), 100 seconds (P1b & P2b), 180 seconds (P1c & P2c), 240 seconds(P1d & P2d), 360 seconds (P1e & P2e), and 420 seconds (P1f & P2f),respectively. These results demonstrate that even after 420 seconds ofreaction, it was possible to observe the symmetric stretching vibrationband between 2092 and 2098 cm⁻¹ assigned to the N≡N, suggesting thepresence of unreacted azide groups in the final product.

In a different approach, the presence of molecular coupling agents inthe blends with the polymeric coupling agent appeared to trigger theformation of the nitrene species in a shorter reaction time. Thus, acoupling reaction was carried out between a HPP of melt flow of 2.0dg/min and a polymeric coupling agent blend B3 and B4 under theconditions described in Example 8. The product of the reaction wascollected after 45 seconds for samples P3a-B3 and P3a-B4 and the N≡Nsymmetric stretching vibration band was not detected by FTIR, as shownin FIG. 14.

What is claimed is:
 1. A long-chain branched polymer, comprising apolyolefin base polymer that contains one or more long-chain branchesformed by covalently bonding one or more polymeric coupling agents atone or more binding sites along the polyolefin base polymer chain,wherein, prior to covalently bonding to the polyolefin base polymer, thepolymeric coupling agents are modified polyolefins having a reactivecoupling group at one or more terminal ends of the modified polyolefinchain.
 2. The long-chain branched polymer of claim 1, wherein themodified polyolefin of the coupling agent has a number average molecularweight of less than 20,000 g/mol.
 3. The long-chain branched polymer ofclaim 1, wherein the polyolefin base polymer is a polymer or copolymerof one or more olefins having from 2 to 12 carbons and a number averagemolecular weight of greater than 50,000 g/mol.
 4. The long-chainbranched polymer of claim 1, wherein the polyolefin base polymer ispolyethylene, polypropylene, a copolymer thereof, or polymer blendscontaining polyethylene and/or polypropylene.
 5. A long-chain branchedpolymer, comprising a polyolefin base polymer that contains one or morelong-chain branches formed by covalently bonding one or more polymericcoupling agents at one or more binding sites along the polyolefin basepolymer chain, wherein at least one long-chain branch is formed byself-coupling two or more polymeric coupling agents.
 6. A long-chainbranched polymer, comprising a polyolefin base polymer that contains oneor more long-chain branches formed by covalently bonding one or morepolymeric coupling agents at one or more binding sites along thepolyolefin base polymer chain, wherein said long-chain branched polymeris a crosslinked or hyperbranched polymer.
 7. The long-chain branchedpolymer of claim 1, wherein the reactive coupling group is different ateach terminal end of the modified polyolefin chain.
 8. The long-chainbranched polymer of claim 1, wherein the reactive coupling groups ateach terminal end of the modified polyolefin chain are the same.
 9. Thelong-chain branched polymer of claim 1, wherein the reactive couplinggroup residing at one or more terminal ends of the modified polyolefinchain is an azide group.
 10. The long-chain branched polymer of claim 9,wherein the reactive coupling group at one terminal end of the modifiedpolyolefin chain is an azide group, and the other terminal ends of themodified polyolefin chain contain one or more different reactivecoupling groups or non-reactive functional groups.
 11. A long-chainbranched polymer, comprising a polyolefin base polymer that contains oneor more long-chain branches formed by covalently bonding one or morepolymeric coupling agents at one or more binding sites along thepolyolefin base polymer chain, wherein, prior to covalently bonding tothe polyolefin base polymer, the polymeric coupling agents are modifiedpolyolefins having a reactive coupling group at one or more terminalends of the modified polyolefin chain, and wherein the reactive couplinggroup residing at one terminal end of the modified polyolefin chain isan azide group, and the other terminal ends of the modified polyolefinchain contain one or more non-azide reactive coupling group or thenon-reactive functional group selected from the group consisting of aperoxide, alkyl borane, halogen, thiol, amine, aldehyde, alcohol,carboxylic acid, ester, isocyanate, silanes, phosphorous-containinggroup, dithioester, dithiocarbamate, dithiocarbonate, trithiocarbonate,alkoxyamine, aryl sulfonyl halide, vinyl, diene, porphyrin, dye, orderivatives thereof.
 12. The long-chain branched polymer of claim 3,wherein the one or more olefins are selected from the group consistingof ethylene; propylene; 1-butene; 2-butene; 1,3-butadiene; 1-pentene;1,3-pentadiene; 1,4-pentadiene; 3-methyl-1-butene;3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene; 1-hexene;1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene; 4-methyl-1-pentene;3-methyl-1-pentene; 3-methyl-1,5-hexadiene; 3,4-dimethyl-1,5-hexadiene;4,6-dimethyl-1-heptene; 1,3-heptadiene; 1,4-heptadiene; 1,5-heptadiene;1,6-heptadiene; 1-octene; 1,3-octadiene; 1,4-octadiene; 1,5-octadiene;1,6-octadiene; 1,7-octadiene; 1-decene; 1-undecene; 1-dodecene;1-tetradecene; 1-hexadecene; 1-octadecene; 1-eicocene, and combinationsthereof.
 13. A long-chain branched polymer, comprising a polyolefin basepolymer that contains one or more long-chain branches formed bycovalently bonding one or more polymeric coupling agents at one or morebinding sites along the polyolefin base polymer chain, wherein thepolyolefin base polymer is a polymer blend containing ethylene propylenerubber (EPR).
 14. The long-chain branched polymer of claim 1, whereinthe radius of gyration (R_(g)) of the long-chain branched polymer isdecreased relative to the radius of gyration (R_(g)) of the polyolefinbase polymer prior to covalently bonding the one or more polymericcoupling agents to form the long-chain branches.
 15. The long-chainbranched polymer of claim 1, wherein the intrinsic viscosity ([η]) ofthe long-chain branched polymer is increased relative to the intrinsicviscosity ([η]) of the polyolefin base polymer prior to covalentlybonding the one or more polymeric coupling agents to form the long-chainbranches.
 16. The long-chain branched polymer of claim 1, wherein themelt tensile of the long-chain branched polymer is increased relative tothe melt tensile of the polyolefin base polymer prior to covalentlybonding the one or more polymeric coupling agents to form the long-chainbranches.
 17. The long-chain branched polymer of claim 16, wherein themelt tensile of the long-chain branched polymer is increased by at least0.1N relative to the melt tensile of the polyolefin base polymer priorto covalently bonding the one or more polymeric coupling agents to formthe long-chain branches.
 18. The long-chain branched polymer of claim 5,wherein, prior to covalently bonding to the polyolefin base polymer, thepolymeric coupling agents are modified polyolefins having a reactivecoupling group at one or more terminal ends of the modified polyolefinchain.
 19. The long-chain branched polymer of claim 18, wherein themodified polyolefin of the coupling agent has a number average molecularweight of less than 20,000 g/mol.
 20. The long-chain branched polymer ofclaim 5, wherein the polyolefin base polymer is a polymer or copolymerof one or more olefins having from 2 to 12 carbons and a number averagemolecular weight of greater than 50,000 g/mol.
 21. The long-chainbranched polymer of claim 5, wherein the polyolefin base polymer ispolyethylene, polypropylene, a copolymer thereof, or polymer blendscontaining polyethylene and/or polypropylene.
 22. The long-chainbranched polymer of claim 18, wherein the reactive coupling groupresiding at one or more terminal ends of the modified polyolefin chainis an azide group.
 23. The long-chain branched polymer of claim 20,wherein the one or more olefins are selected from the group consistingof ethylene; propylene; 1-butene; 2-butene; 1,3-butadiene; 1-pentene;1,3-pentadiene; 1,4-pentadiene; 3-methyl-1-butene;3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene; 1-hexene;1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene; 4-methyl-1-pentene;3-methyl-1-pentene; 3-methyl-1,5-hexadiene; 3,4-dimethyl-1,5-hexadiene;4,6-dimethyl-1-heptene; 1,3-heptadiene; 1,4-heptadiene; 1,5-heptadiene;1,6-heptadiene; 1-octene; 1,3-octadiene; 1,4-octadiene; 1,5-octadiene;1,6-octadiene; 1,7-octadiene; 1-decene; 1-undecene; 1-dodecene;1-tetradecene; 1-hexadecene; 1-octadecene; 1-eicocene, and combinationsthereof.
 24. The long-chain branched polymer of claim 6, wherein, priorto covalently bonding to the polyolefin base polymer, the polymericcoupling agents are modified polyolefins having a reactive couplinggroup at one or more terminal ends of the modified polyolefin chain. 25.The long-chain branched polymer of claim 24, wherein the modifiedpolyolefin of the coupling agent has a number average molecular weightof less than 20,000 g/mol.
 26. The long-chain branched polymer of claim6, wherein the polyolefin base polymer is a polymer or copolymer of oneor more olefins having from 2 to 12 carbons and a number averagemolecular weight of greater than 50,000 g/mol.
 27. The long-chainbranched polymer of claim 6, wherein the polyolefin base polymer ispolyethylene, polypropylene, a copolymer thereof, or polymer blendscontaining polyethylene and/or polypropylene.
 28. The long-chainbranched polymer of claim 24, wherein the reactive coupling groupresiding at one or more terminal ends of the modified polyolefin chainis an azide group.
 29. The long-chain branched polymer of claim 26,wherein the one or more olefins are selected from the group consistingof ethylene; propylene; 1-butene; 2-butene; 1,3-butadiene; 1-pentene;1,3-pentadiene; 1,4-pentadiene; 3-methyl-1-butene;3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene; 1-hexene;1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene; 4-methyl-1-pentene;3-methyl-1-pentene; 3-methyl-1,5-hexadiene; 3,4-dimethyl-1,5-hexadiene;4,6-dimethyl-1-heptene; 1,3-heptadiene; 1,4-heptadiene; 1,5-heptadiene;1,6-heptadiene; 1-octene; 1,3-octadiene; 1,4-octadiene; 1,5-octadiene;1,6-octadiene; 1,7-octadiene; 1-decene; 1-undecene; 1-dodecene;1-tetradecene; 1-hexadecene; 1-octadecene; 1-eicocene, and combinationsthereof.
 30. The long-chain branched polymer of claim 11, wherein themodified polyolefin of the coupling agent has a number average molecularweight of less than 20,000 g/mol.
 31. The long-chain branched polymer ofclaim 11, wherein the polyolefin base polymer is a polymer or copolymerof one or more olefins having from 2 to 12 carbons and a number averagemolecular weight of greater than 50,000 g/mol.
 32. The long-chainbranched polymer of claim 11, wherein the polyolefin base polymer ispolyethylene, polypropylene, a copolymer thereof, or polymer blendscontaining polyethylene and/or polypropylene.
 33. The long-chainbranched polymer of claim 31, wherein the one or more olefins areselected from the group consisting of ethylene; propylene; 1-butene;2-butene; 1,3-butadiene; 1-pentene; 1,3-pentadiene; 1,4-pentadiene;3-methyl-1-butene; 3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene;1-hexene; 1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene;4-methyl-1-pentene; 3-methyl-1-pentene; 3-methyl-1,5-hexadiene;3,4-dimethyl-1,5-hexadiene; 4,6-dimethyl-1-heptene; 1,3-heptadiene;1,4-heptadiene; 1,5-heptadiene; 1,6-heptadiene; 1-octene; 1,3-octadiene;1,4-octadiene; 1,5-octadiene; 1,6-octadiene; 1,7-octadiene; 1-decene;1-undecene; 1-dodecene; 1-tetradecene; 1-hexadecene; 1-octadecene;1-eicocene, and combinations thereof.
 34. The long-chain branchedpolymer of claim 13, wherein, prior to covalently bonding to thepolyolefin base polymer, the polymeric coupling agents are modifiedpolyolefins having a reactive coupling group at one or more terminalends of the modified polyolefin chain.
 35. The long-chain branchedpolymer of claim 34, wherein the modified polyolefin of the couplingagent has a number average molecular weight of less than 20,000 g/mol.36. The long-chain branched polymer of claim 13, wherein the polyolefinbase polymer is a polymer or copolymer of one or more olefins havingfrom 2 to 12 carbons and a number average molecular weight of greaterthan 50,000 g/mol.
 37. The long-chain branched polymer of claim 34,wherein the reactive coupling group residing at one or more terminalends of the modified polyolefin chain is an azide group.
 38. Thelong-chain branched polymer of claim 36, wherein the one or more olefinsare selected from the group consisting of ethylene; propylene; 1-butene;2-butene; 1,3-butadiene; 1-pentene; 1,3-pentadiene; 1,4-pentadiene;3-methyl-1-butene; 3-methyl-1,4-pentadiene; 3,3-dimethyl-1,4-pentadiene;1-hexene; 1,3-hexadiene; 1,4-hexadiene; 1,5-hexadiene;4-methyl-1-pentene; 3-methyl-1-pentene; 3-methyl-1,5-hexadiene;3,4-dimethyl-1,5-hexadiene; 4,6-dimethyl-1-heptene; 1,3-heptadiene;1,4-heptadiene; 1,5-heptadiene; 1,6-heptadiene; 1-octene; 1,3-octadiene;1,4-octadiene; 1,5-octadiene; 1,6-octadiene; 1,7-octadiene; 1-decene;1-undecene; 1-dodecene; 1-tetradecene; 1-hexadecene; 1-octadecene;1-eicocene, and combinations thereof.